Substituent effects on stability of ketenimines

An isodesmic reaction was designed to study substituent effects on the stab ility of ketenimines. A good correlation (Delta E = -11.31 chi(BE) + 31.07) between substituent group electronegativity and the stability of ketenimin es has been found. Electropositive substituents stabilize ketenimines while electronegative substituents destabilize ketenimines. Ketenimines gain ext ra stabilization when their substituents are pi accepters, such as AlH2, BH 2, O=CH-, HO2C-, CN, NO2, and HSO2, resulting in the existence of cyano-cat ion resonance structures. An ynamine resonance structure plays an important role in ketenimine with a lithium substituent.